A flow cytometer is a biological cell (bio-cell) analysis and counting instrument. It is used to analyze the physical and chemical characteristics of bio-cells in a fluid as they pass through one or more laser beams from lasers. The bio-cells are fluorescently labeled and then excited by the lasers to emit light at correspondent wavelengths. The fluorescence and the scattered light can be detected and measured to determine various properties of the cells. Up to thousands of cells per second can be analyzed by a flow cytometer.
Generally, a flow cytometer includes components of fluidics, optics and electronics. The fluidics system is to line up and transport cells in a stream of fluid to the laser beams where they are excited. Any cell of submicron to over 100-μm in size can be analyzed. The optics system consists of lasers which excite the cells in the stream and get scattered. Fluorescent labeled cells emit fluorescence, which is collected by a lens. The laser light scattered by the cells is captured at forward and side directions. Optical steering mirrors direct the light signals to the correspondent detectors, such as a photomultiplier tube (PMT), an avalanche photodiode (APD) or a PIN diode (diode with a wide, undoped intrinsic semiconductor region between a p-type semiconductor and an n-type semiconductor region). An electronics system converts the light signals detected into electronic signals for a computer to process. Data are collected on each cell. The characteristics of the cells are determined based on their fluorescent and light scattering properties. A large number of cells are analyzed to draw information on the heterogeneity and different subsets within the cell populations. The data are usually presented in the form of single parameter histograms or as plots of correlated parameters, which are referred to as cytograms, displaying data in the form of a dot plot, a contour plot, or a density plot.
Flow cytometry has been widely used in the diagnosis of leukemia and human immunodeficiency virus (HIV). Flow cytometry is also commonly used in basic research and clinical trials, such as molecular biology, immunology, and pathology. Flow cytometry has become an important lab process in transplantation, oncology, hematology, genetics and prenatal diagnosis. Flow cytometry can also be used to help identify cell surface protein variants.
Conventional flow cytometers are large in size due to their complicated system construction. Bench top space is always precious in a lab, especially when many diagnostic instruments compete for presence in the lab and the many tests that must be accommodated to service the various clients and patients. In a single core lab, there are normally many flow cytometers deployed for service where the size of the flow cytometer becomes of greater concern.